WO2024065808A1

WO2024065808A1 - Battery, preparation method therefor, and electrical apparatus comprising same

Info

Publication number: WO2024065808A1
Application number: PCT/CN2022/123586
Authority: WO
Inventors: 张翠平; 韩昌隆; 范朋; 张哲�
Original assignee: 宁德时代新能源科技股份有限公司
Priority date: 2022-09-30
Filing date: 2022-09-30
Publication date: 2024-04-04
Also published as: CN117015883A

Abstract

The present application provides a battery, a preparation method therefor, and an electrical apparatus comprising same. The battery comprises a positive electrode pole piece and an electrolyte. The positive electrode pole piece comprises a positive electrode current collector, and the positive electrode current collector comprises a conductive layer. The electrolyte comprises a first anion and a second anion, the first anion comprising an anion selected from hexafluorophosphate anions, and the second anion comprising one or more anions selected from an anion represented by formula 1 and an anion represented by formula 2. The thickness of the conductive layer is H1 μm, the concentration of the first anion in the electrolyte is C1 mol/L, and the concentration of the second anion is C2 mol/L. Furthermore, the battery satisfies 0.2×(C2/C1)≤H1≤(C2/C 1)+3. The present application can cause a battery to have excellent electrochemical performance, while improving battery safety performance.

Description

Battery, method for preparing the same, and electrical device containing the same

Technical Field

The present application belongs to the field of battery technology, and specifically relates to a battery, a preparation method thereof, and an electrical device containing the same.

Background technique

In recent years, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. With the application and promotion of batteries, their safety issues have received more and more attention. If the safety of the battery cannot be guaranteed, the battery cannot be used. Therefore, how to enhance the safety performance of the battery without affecting the electrochemical performance of the battery is a technical problem that needs to be solved urgently.

Summary of the invention

The purpose of the present application is to provide a battery, a preparation method thereof, and an electrical device comprising the same, which can reduce the impact of positive electrode collector corrosion on battery safety and electrochemical performance, thereby improving battery safety while also giving the battery good electrochemical performance.

In a first aspect, the present application provides a battery, comprising a positive electrode plate and an electrolyte, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, the positive electrode current collector comprises a conductive layer, the electrolyte comprises a solvent and a solute, the solute is an ionic salt formed by a cation and an anion, the cation comprises one or more selected from alkali metal cations and alkaline earth metal cations, and optionally comprises one or more selected from lithium ions, sodium ions and potassium ions, the anion comprises a first anion and a second anion, the first anion comprises a hexafluorophosphate anion, the second anion comprises one or more selected from anions represented by Formula 1 and anions represented by Formula 2, R ₁ , R ₂ , and R ₃ each independently represent a fluorine atom or a C1-C5 fluorine-containing alkyl group, R ₁ and R ₂ can also be bonded to form a ring, the thickness of the conductive layer is H ₁ μm, the concentration of the first anion in the electrolyte is C ₁ mol/L, the concentration of the second anion is C ₂ mol/L, and the battery satisfies 0.2×(C ₂ /C ₁ )≤H ₁ ≤(C ₂ /C ₁ )+3.

The inventors of the present application surprisingly discovered through a large number of experiments that by adjusting the relationship between the thickness of the conductive layer H ₁ μm, the concentration of the first anion C ₁ mol/L and the concentration of the second anion C ₂ mol/L to satisfy 0.2×(C ₂ /C ₁ )≤H ₁ ≤(C ₂ /C ₁ )+3, the influence of corrosion of the conductive layer on the safety performance and electrochemical performance of the battery can be reduced, thereby improving the safety performance of the battery while giving the battery good electrochemical performance, for example, the battery can have a longer service life.

In any embodiment of the present application, 0.2×(C ₂ /C ₁ )+0.2≤H ₁ ≤(C ₂ /C ₁ )+2. Thus, the influence of corrosion of the conductive layer on the safety performance and electrochemical performance of the battery can be further reduced.

In any embodiment of the present application, 0.2≤H ₁ ≤8, and optionally, 1≤H ₁ ≤5. Thus, the battery safety performance can be improved while the battery has good electrochemical performance.

In any embodiment of the present application, 0.1≤C ₁ ≤1. The first anion helps to improve the ion conductivity of the electrolyte, accelerate ion transport, and improve the capacity of the battery.

In any embodiment of the present application, 0.1≤C ₂ ≤1.5, optionally, 0.5≤C ₂ ≤1.5. The second anion can increase the ion dissociation degree of the electrolyte, reduce the viscosity of the electrolyte, and increase the ionic conductivity of the electrolyte. In addition, the second anion has the characteristics of good high temperature resistance and non-hydrolysis, thereby improving the cycle performance of the battery.

In any embodiment of the present application, 0.6≤C ₁ +C ₂ ≤2.5, optionally, 0.6≤C ₁ +C ₂ ≤2.0.

In any embodiment of the present application, 0.1≤C ₂ /C ₁ ≤5, optionally, 0.5≤C ₂ /C ₁ ≤5.

When the concentration of the first anion and the concentration of the second anion satisfy 0.6≤C ₁ +C ₂ ≤2.5 and/or 0.1≤C ₂ /C ₁ ≤5, the corrosion of the conductive layer can be inhibited to a certain extent, the safety performance of the battery can be improved, and the battery can maintain excellent cycle performance.

In any embodiment of the present application, the positive electrode current collector further comprises an organic support layer, the conductive layer is disposed on at least one surface of the organic support layer, and the conductive layer is further disposed between the organic support layer and the positive electrode active material layer. This can further improve the safety performance of the battery and avoid thermal runaway caused by short circuit between the positive and negative electrodes.

In any embodiment of the present application, the thickness of the organic support layer is H ₂ μm, and the battery satisfies 0.1≤H ₁ /H ₂ ≤1, and optionally, 0.2≤H ₁ /H ₂ ≤0.6. Thus, the battery safety performance can be improved while the battery has good electrochemical performance.

In any embodiment of the present application, the thickness of the organic support layer is H ₂ μm, 1≤H ₂ ≤10, and optionally, 4≤H ₂ ≤7. Thus, the battery safety performance can be improved while the battery has high energy density.

In any embodiment of the present application, the total thickness of the positive electrode current collector is H ₀ μm, 5≤H ₀ ≤15, optionally, 9≤H ₀ ≤15.

In any embodiment of the present application, the total thickness of the positive electrode current collector is H ₀ μm, the elongation at break of the positive electrode current collector is S ₀ , and the battery satisfies 5S ₀ –(H ₀ /10)≤C ₁ /C ₂ ≤100S ₀ +(H ₀ /9). When the battery also satisfies 5S ₀ –(H ₀ /10)≤C ₁ /C ₂ ≤100S ₀ +(H ₀ /9), the influence of corrosion of the conductive layer on the safety performance and electrochemical performance of the battery can be further reduced, thereby enabling the battery to have better safety performance and electrochemical cycle performance.

In any embodiment of the present application, 2%≤S ₀ ≤3.5%.

In any embodiment of the present application, the organic support layer includes one or more of a polymer material and a polymer-based composite material.

In any embodiment of the present application, the polymer material includes one or more selected from polyolefins, polyalkynes, polyesters, polycarbonates, polyacrylates, polyamides, polyimides, polyethers, polyols, polysulfones, polysulfur nitrides, polysaccharide polymers, amino acid polymers, aromatic ring polymers, aromatic heterocyclic polymers, epoxy resins, phenolic resins, polyurethanes, thermoplastic elastomers, rubbers, derivatives of the above materials, crosslinked products of the above materials, and copolymers of the above materials, and optionally includes one or more selected from polyethylene, polypropylene, polystyrene, polyvinyl chloride. one or more of polyolefins, polyvinylidene fluoride, polytetrafluoroethylene, polyacetylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polymethyl methacrylate, polycaprolactam, polyhexamethylene adipamide, poly(p-phenylene terephthalamide), polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, polyvinyl alcohol, poly-4-hydroxybenzoic acid, poly-2-hydroxy-6-naphthoic acid, polyaniline, polypyrrole, polythiophene, polyphenylene, sodium polystyrene sulfonate, cellulose, starch, silicone rubber, acrylonitrile-butadiene-styrene copolymer, derivatives of the above materials, crosslinked products of the above materials, and copolymers of the above materials,

In any embodiment of the present application, the polymer-based composite material includes the polymer material and an additive, and the additive includes one or more selected from metal materials and inorganic non-metallic materials.

In any embodiment of the present application, the conductive layer includes one or more selected from metal materials, optionally including one or more selected from aluminum, silver, nickel, titanium, stainless steel, aluminum alloy, silver alloy, nickel alloy and titanium alloy.

In any embodiment of the present application, R ₁ , R ₂ , and R ₃ each independently represent a fluorine atom, a trifluoromethyl group, a pentafluoroethyl group, or a heptafluoropropyl group.

In any embodiment of the present application, R ₁ and R ₂ are the same.

In any embodiment of the present application, the electrolyte further comprises a third anion, and the third anion comprises one or more selected from tetrafluoroborate anion, difluorooxalate borate anion, dioxalate borate anion, difluorophosphate anion, difluorobisoxalate phosphate anion and tetrafluorooxalate phosphate anion. These anions contribute to forming a protective film with excellent performance on the surface of the positive electrode and/or the negative electrode, thereby further improving at least one of the cycle performance, rate performance, storage performance, etc. of the battery.

In any embodiment of the present application, the battery further comprises a negative electrode sheet and a separator, and the separator is located between the positive electrode sheet and the negative electrode sheet.

A second aspect of the present application provides a method for preparing a battery, comprising the

following steps

1 and 2.

Step 1: Assemble the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte into a battery.

The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, and the positive electrode current collector includes a conductive layer.

The electrolyte includes a solvent and a solute, the solute is an ionic salt formed by cations and anions, the cations include one or more selected from alkali metal cations and alkaline earth metal cations, and optionally include one or more selected from lithium ions, sodium ions and potassium ions, the anions include a first anion and a second anion, the first anion includes a hexafluorophosphate anion, the second anion includes one or more selected from anions represented by formula 1 and anions represented by formula 2, R ₁ , R ₂ , and R ₃ each independently represent a fluorine atom or a C1-C5 fluorinated alkyl group, and R ₁ and R ₂ may also be bonded to form a ring.

The thickness of the conductive layer is H ₁ μm, the concentration of the first anion in the electrolyte is C ₁ mol/L, and the concentration of the second anion in the electrolyte is C ₂ mol/L.

Step 2, selecting from the batteries obtained in step 1 batteries that satisfy 0.2×(C ₂ /C ₁ )≤H ₁ ≤(C ₂ /C ₁ )+3, and optionally batteries that satisfy 0.2×(C ₂ /C ₁ )+0.2≤H ₁ ≤(C ₂ /C ₁ )+2.

In any embodiment of the present application, the method further comprises: step 3, selecting batteries satisfying at least one of the following conditions (1) to (9) from the batteries obtained in step 2,

(1) 0.2 ≤ H ₁ ≤ 8,

(2)1≤H ₁ ≤5,

(3) 0.1 ≤ C ₁ ≤ 1,

(4) 0.1 ≤ C ₂ ≤ 1.5,

(5) 0.5 ≤ C ₂ ≤ 1.5,

(6) 0.6 ≤ C ₁ + C ₂ ≤ 2.5,

(7) 0.6 ≤ C ₁ + C ₂ ≤ 2.0,

(8) 0.1 ≤ C ₂ /C ₁ ≤ 5,

(9)0.5≤C ₂ /C ₁ ≤5.

In any embodiment of the present application, in step 1, the positive electrode current collector further includes an organic support layer, the conductive layer is disposed on at least one surface of the organic support layer, and the conductive layer is also disposed between the organic support layer and the positive electrode active material layer, the thickness of the organic support layer is H ₂ μm, the total thickness of the positive electrode current collector is H ₀ μm, and the elongation at break of the positive electrode current collector is S ₀ .

In any embodiment of the present application, the method further comprises: step 4, selecting a battery satisfying at least one of the following conditions (1) to (8) from the batteries obtained in step 2 or step 3,

(1) 5S ₀ – (H ₀ /10) ≤ C ₁ /C ₂ ≤ 100S ₀ + (H ₀ /9),

(2) 0.1 ≤ _{H 1} /H ₂ ≤ 1,

(3) 0.2 ≤ _{H 1} /H ₂ ≤ 0.6,

(4) _1≤H2≤10 ,

(5) _4≤H2≤7 ,

(6)5≤H ₀ ≤15,

(7) 9≤H ₀ ≤15,

(8) 2% ≤ _{S 0} ≤ 3.5%.

The battery obtained by the preparation method of the present application has high safety performance and good electrochemical performance.

A third aspect of the present application provides an electrical device, comprising the battery of the first aspect of the present application or a battery prepared by the method of the second aspect of the present application.

The inventors of the present application surprisingly found through a large number of experiments that by adjusting the relationship between the thickness of the conductive layer H ₁ μm, the concentration of the first anion C ₁ mol/L and the concentration of the second anion C ₂ mol/L to satisfy 0.2×(C ₂ /C ₁ )≤H ₁ ≤(C ₂ /C ₁ )+3, the influence of the corrosion of the conductive layer on the safety performance and electrochemical performance of the battery can be reduced, thereby improving the safety performance of the battery while giving the battery good electrochemical performance. The electrical device of the present application includes the battery provided by the present application, and thus has at least the same advantages as the battery.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some implementation methods of the present application, and for ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

FIG. 1 is a schematic diagram of a battery cell according to an embodiment of the present application.

FIG. 2 is an exploded schematic diagram of an embodiment of a battery cell of the present application.

FIG. 3 is a schematic diagram of an embodiment of a battery module of the present application.

FIG. 4 is a schematic diagram of an embodiment of a battery pack of the present application.

FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .

FIG. 6 is a schematic diagram of an embodiment of a positive electrode plate of the present application.

FIG. 7 is a schematic diagram of another embodiment of the positive electrode plate of the present application.

FIG8 is a schematic diagram of an embodiment of an electrical device including the battery of the present application as a power source.

In the drawings, the drawings may not be drawn according to the actual scale. The reference numerals are as follows: 101 positive electrode current collector, 102 positive electrode active material layer, 1011 conductive layer, 1012 organic support layer, 1 battery pack, 2 upper case, 3 lower case, 4 battery module, 5 battery cell, 51 housing, 52 electrode assembly, 53 cover plate.

Detailed ways

Hereinafter, the battery of the present application, its preparation method, and the implementation mode of the electric device containing the battery of the present application are specifically disclosed in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a specific parameter, it is understood that the range of 60-110 and 80-120 is also expected. In addition, if the

minimum range values

1 and 2 are listed, and if the

maximum range values

3, 4 and 5 are listed, the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just the abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

If not otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

Unless otherwise specified, all technical features and optional technical features of the present application may be combined with each other to form a new technical solution, and such a technical solution should be deemed to be included in the disclosure of the present application.

If not otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

If there is no special explanation, the "include" and "comprising" mentioned in this application represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

In the present application, the terms "plurality" and "multiple" refer to two or more.

In order to improve the safety performance of the battery, in addition to improving the thermal safety performance of the material itself, the design of the electrode assembly is currently being optimized, such as using a composite current collector. The composite current collector is usually an organic support layer (or insulating layer) arranged between two conductive layers (such as metal layers), which can improve the safety performance of the battery and avoid thermal runaway problems caused by short circuits between the positive and negative electrodes. However, in order to avoid sacrificing the energy density of the battery and to reduce production costs, the prior art usually reduces the thickness of the conductive layer.

When the electrolyte contains fluorinated sulfonyl imide salts and fluorinated sulfonates, the electrolyte will corrode the conductive layer (for example, aluminum foil). When the conductive layer is thicker, the degree of corrosion of the electrolyte is not enough to have a significant impact on the performance of the battery. However, the inventors of the present application found during the research process that when the thickness of the conductive layer is reduced, the slight corrosion of the electrolyte will have a significant impact on the performance of the battery. At this time, the fluorinated sulfonyl imide salts, fluorinated sulfonates, etc. in the electrolyte will undergo an oxidation reaction at the positive electrode, and their oxidation products will combine with the metal (such as aluminum) in the conductive layer, and the combined products will further dissolve into the electrolyte, thereby leaving corrosion pits on the surface of the conductive layer, which may cause the positive electrode to be fragmented, and even seriously threaten the safety performance and service life of the battery.

Battery

In view of the above problems, the present application provides a battery including a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. The present application has no particular restrictions on the type of battery. For example, the battery may be a lithium ion battery, a sodium ion battery, etc. In particular, the battery may be a lithium ion secondary battery.

The battery mentioned in the embodiments or implementations of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module or a battery pack. A battery cell is the smallest unit that makes up a battery, which can realize the function of charging and discharging alone. The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. Figure 1 is a battery cell 5 of a square structure as an example.

In some embodiments, the battery cell includes an electrode assembly, and the single cell may further include an outer package. The electrode assembly may be made of a positive electrode sheet, a negative electrode sheet, and a separator by a winding process and/or a lamination process, and the outer package may be used to encapsulate the above-mentioned electrode assembly and the electrolyte. The outer package may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

In some embodiments, as shown in FIG. 2 , the outer package may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The electrode assembly 52 is encapsulated in the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to demand.

In some embodiments of the present application, battery cells can be assembled into a battery module, and the number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. FIG. 3 is a schematic diagram of a battery module 4 as an example. As shown in FIG. 3, in the battery module 4, multiple battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other manner. The multiple battery cells 5 can be further fixed by fasteners.

Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

In some embodiments, the battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack. Figures 4 and 5 are schematic diagrams of a battery pack 1 as an example. As shown in Figures 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4. Multiple battery modules 4 can be arranged in the battery box in any manner.

[Electrolyte]

The electrolyte includes a solvent and a solute, the solute is an ionic salt formed by cations and anions, the cations include one or more selected from alkali metal cations and alkaline earth metal cations, the anions include a first anion and a second anion, the first anion includes a hexafluorophosphate anion, the second anion includes one or more selected from anions represented by Formula 1 (fluorinated sulfonyl imide anions) and anions represented by Formula 2 (fluorinated sulfonate anions), R ₁ , R ₂ , and R ₃ each independently represent a fluorine atom or a C1-C5 fluorinated alkyl group, and R ₁ and R ₂ may also be bonded to form a ring.

The most widely used non-aqueous electrolyte system in commercial applications is a mixed carbonate solution of hexafluorophosphate. However, hexafluorophosphate has poor thermal stability in high temperature environments and will decompose to produce _PF5 at higher temperatures. _PF5 has strong Lewis acidity and will react with the lone pair of electrons on the oxygen atoms in the solvent molecules to decompose the solvent. In addition, _PF5 is highly sensitive to trace amounts of water in non-aqueous electrolytes and will produce HF when it comes into contact with water. Fluorinated sulfonyl imide salts and fluorinated sulfonates have the advantages of high thermal stability and insensitivity to water. Using them in combination with hexafluorophosphate can greatly improve the thermal stability and cycle performance of the battery.

In the present application, a "fluorinated alkyl group" refers to a group in which at least one hydrogen atom in an alkyl group is substituted by a fluorine atom, and the fluorinated alkyl group may be a partially fluorinated alkyl group or a perfluoroalkyl group.

In some embodiments, optionally, R ₁ , R ₂ , and R ₃ each independently represent a fluorine atom, a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, or a nonafluorobutyl group.

In some embodiments, optionally, the second anion includes one or more selected from a bisfluorosulfonyl imide anion, a bis(trifluoromethylsulfonyl) imide anion, a bis(pentafluoroethylsulfonyl) imide anion, a bis(nonafluorobutylsulfonyl) imide anion, a (trifluoromethylsulfonyl)(nonafluorobutylsulfonyl) imide anion, a (fluorosulfonyl)(trifluoromethylsulfonyl) imide anion, a perfluoropropane disulfonyl imide anion, a fluorosulfonate anion and a trifluoromethylsulfonate anion.

In some embodiments, optionally, R ₁ and R ₂ are the same.

In the present application, the cation includes one or more selected from alkali metal cations and alkaline earth metal cations. Optionally, the alkali metal cation includes one or more selected from lithium ions, sodium ions and potassium ions. Optionally, the alkaline earth metal cation includes one or more selected from magnesium ions, calcium ions or a combination thereof.

In some embodiments, optionally, the cation includes one or more selected from lithium ions, sodium ions and potassium ions, and more optionally includes lithium ions, sodium ions or a combination thereof.

In some embodiments, the electrolyte further includes a third anion, and the third anion includes one or more selected from tetrafluoroborate anion (BF ₄ ^- ), difluorooxalatoborate anion (DFOB ^- ), dioxalatoborate anion (BOB ^- ), difluorophosphate anion (PO ₂ F ₂ ^- ), difluorobisoxalatophosphate anion (DFOP ^- ) and tetrafluorooxalatophosphate anion (TFOP ^- ). These anions help to form a protective film with excellent performance on the surface of the positive electrode and/or the negative electrode, thereby further improving at least one of the cycle performance, rate performance, storage performance, etc. of the battery.

The present application has no specific restrictions on the type of the solvent, and can be selected according to actual needs. In some embodiments, the solvent may include one or more selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), cyclopentane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl sulfate (DTD) and 1,3-propane sultone (PS).

In some embodiments, the electrolyte may further include additives, for example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, additives that improve battery low temperature power performance, etc.

In the present application, each component in the electrolyte and its specific content can be measured according to methods known in the art. For example, it can be measured by gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), inductively coupled plasma optical emission spectroscopy (ICP-OES).

[Positive electrode]

The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

In some embodiments, the positive electrode current collector includes a conductive layer.

In some embodiments, the positive electrode current collector may be composed only of a conductive layer, or, in some embodiments, the positive electrode current collector may include an organic support layer in addition to a conductive layer, wherein the conductive layer is disposed on at least one surface of the organic support layer, and the conductive layer is also disposed between the organic support layer and the positive electrode active material layer. For example, the organic support layer has two surfaces opposite to each other in its thickness direction, and the conductive layer is disposed on any one or both of the two opposite surfaces of the organic support layer to form a composite current collector. This can further improve the safety performance of the battery and avoid thermal runaway problems caused by short circuits between the positive and negative electrodes.

When the positive electrode current collector is composed only of a conductive layer, the thickness of the conductive layer decreases, the cross-sectional area decreases, and the resistance increases, thereby improving the safety performance of the battery and increasing the energy density of the battery; in addition, after the thickness of the conductive layer is reduced, the flexibility is better, thereby reducing the risk of positive electrode segmental tape (such as winding tape breakage) that may occur during battery preparation. However, at this time, the electronic conduction characteristics of the positive electrode current collector deteriorate, and the battery polarization is easily increased, which is detrimental to the cycle performance and rate performance of the battery, and its effect on improving the safety performance of the battery is weak.

In some embodiments, optionally, the positive electrode current collector includes an organic support layer and a conductive layer disposed on at least one surface of the organic support layer, and the conductive layer is disposed between the organic support layer and the positive electrode active material layer, thereby significantly improving the battery safety performance.

In the present application, the conductive layer may be directly disposed on at least one surface of the organic support layer, or may be indirectly disposed on at least one surface of the organic support layer, for example, other layers may be disposed between the conductive layer and the organic support layer.

In some embodiments, the thickness of the conductive layer is H ₁ μm, the concentration of the first anion in the electrolyte is C ₁ mol/L, the concentration of the second anion is C ₂ mol/L, and the battery satisfies 0.2×(C ₂ /C ₁ )≤H ₁ ≤(C ₂ /C ₁ )+3.

Compared with the first anion, the second anion (fluorinated sulfonyl imide anion and/or fluorinated sulfonate anion) in the electrolyte has the advantages of high thermal stability and insensitivity to water, which can improve the ion dissociation degree of the electrolyte, improve the ionic conductivity of the electrolyte, and thus improve the cycle performance of the battery. However, during the charging process, the second anion will undergo an oxidation reaction at the positive electrode, and its oxidation product will combine with the metal (such as aluminum) in the conductive layer, and the combined product will further dissolve into the electrolyte, thereby causing corrosion of the conductive layer.

In particular, when the positive electrode current collector uses only a thinner conductive layer, or the positive electrode current collector uses a composite current collector formed by a thinner conductive layer and an organic support layer, since the conductive layer is thinner in the thickness direction than the traditional positive electrode current collector (for example, the thickness is about 12μm-20μm), its ability to withstand electrolyte corrosion is weaker, which leads to a more significant impact of the positive electrode current collector corrosion on the safety performance and electrochemical performance of the battery, for example, corrosion pits may be formed on the surface of the conductive layer of the positive electrode current collector, which will lead to problems such as shortened battery life and significantly reduced safety performance. The decomposition product of the first anion (or hexafluorophosphate) (for example, fluorine-containing lithium salt, etc.) can be deposited on the surface of the conductive layer of the positive electrode current collector, thereby inhibiting the corrosion of the conductive layer by the second anion and playing a role in protecting the conductive layer, but its protective effect on the conductive layer is limited and insufficient to compensate for the corrosion of the conductive layer by the second anion.

Therefore, in the design of the prior art, when the electrolyte does not contain the second anion, the thermal stability of the electrolyte is poor, resulting in poor cycle performance of the battery; when the electrolyte contains the second anion, it will corrode the conductive layer, especially the thinner conductive layer, which will have a serious impact, for example, corrosion pits may be formed on the surface of the thinner conductive layer, which will lead to problems such as shortened battery life and significantly reduced safety performance. However, the current battery needs to use some thinner conductive layers alone as positive electrode current collectors, or use a composite current collector formed by a thinner conductive layer and an organic support layer, etc., to increase the safety performance of the battery.

In some embodiments, optionally, 0.2×(C ₂ /C ₁ )+0.2≤H ₁ ≤(C ₂ /C ₁ )+2. Thus, the influence of corrosion of the conductive layer on the safety performance and electrochemical performance of the battery can be further reduced.

The first anion helps to improve the ionic conductivity of the electrolyte, accelerate ion transport, and improve the capacity of the battery. In some embodiments, the concentration of the first anion in the electrolyte is C ₁ mol/L, optionally, 0.1≤C ₁ ≤1. For example, C ₁ can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 or any range thereof.

The second anion can increase the ion dissociation degree of the electrolyte, reduce the viscosity of the electrolyte, and increase the ionic conductivity of the electrolyte. In addition, the second anion has good high temperature resistance and is not easy to hydrolyze, thereby improving the cycle performance of the battery. In some embodiments, the concentration of the second anion in the electrolyte is C ₂ mol/L, and optionally, 0.1≤C ₂ ≤1.5. For example, C ₂ can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or any range consisting of the above values. More optionally, 0.5≤C ₂ ≤1.5.

In some embodiments, optionally, 0.6≤C ₁ +C ₂ ≤2.5. For example, C ₁ +C ₂ may be 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5 or any range thereof. More optionally, 0.6≤C ₁ +C ₂ ≤2.0.

In some embodiments, optionally, 0.1≤C ₂ /C ₁ ≤5. For example, C ₂ /C ₁ may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 or any range thereof. More optionally, 0.5≤C ₂ /C ₁ ≤5, 1≤C ₂ /C ₁ ≤5.

In some embodiments, optionally, the electrolyte satisfies 0.6≤C ₁ +C ₂ ≤2.5 and 0.1≤C ₂ /C ₁ ≤5 simultaneously. More optionally, the electrolyte satisfies 0.6≤C ₁ +C ₂ ≤2.0 and 0.5≤C ₂ /C ₁ ≤5 simultaneously.

The inventors of the present application have found through a large number of experiments that when the concentration of the first anion and the concentration of the second anion satisfy 0.6≤C ₁ +C ₂ ≤2.5 and/or 0.1≤C ₂ /C ₁ ≤5, the corrosion of the conductive layer can be inhibited to a certain extent, the safety performance of the battery can be improved, and the battery can maintain excellent cycle performance.

In some embodiments, the conductive layer may include one or more selected from metal materials, optionally including one or more selected from aluminum, silver, nickel, titanium, stainless steel, aluminum alloy, silver alloy, nickel alloy and titanium alloy, and more optionally including aluminum or aluminum alloy. Aluminum has good electrical conductivity and flexibility, which is convenient for conducting electrons and processing, and fresh aluminum foil is easily oxidized in the air, thereby forming a protective film on the surface to block corrosion of aluminum by external moisture and air, thereby making the aluminum foil or aluminum alloy foil more stable in thermodynamic properties.

In some embodiments, the organic support layer may include one or more of a polymer material and a polymer-based composite material.

In some embodiments, the polymer material includes one or more selected from polyolefins, polyalkynes, polyesters, polycarbonates, polyacrylates, polyamides, polyimides, polyethers, polyalcohols, polysulfones, polysulfur nitrides, polysaccharide polymers, amino acid polymers, aromatic ring polymers, aromatic heterocyclic polymers, epoxy resins, phenolic resins, polyurethanes, thermoplastic elastomers, rubbers, derivatives of the above materials, crosslinked products of the above materials, and copolymers of the above materials.

Optionally, the polymer material includes polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacetylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polycarbonate (PC), polymethyl methacrylate (PMMA), polycaprolactam (PA6), polyhexamethylene adipamide (PA66), polyterephthalamide (PTFE), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyvinyl chloride (PVDF), polyvinyl chloride (PTFE), polyvinyl chloride (PTFE), polyvinyl chloride (PBT), polyvinyl terephthalate (PEN), polycarbonate (PC), polymethyl methacrylate (PMMA), polycaprolactam (PA6), polyhexamethylene adipamide (PA66), polyterephthalamide (PTFE), polyvinyl chloride (PVDF), polyvinyl chloride ...PVDF), polyvinyl chloride (PVDF), polyvinyl chloride (PVDF), polyvinyl chloride (PVDF), polyvinyl chloride (PVDF), One or more of amine (PPTA), polyoxymethylene (POM), polyphenylene ether (PPO), polyphenylene sulfide (PPS), polyethylene glycol (PEG), polyvinyl alcohol (PVA), poly 4-hydroxybenzoic acid, poly 2-hydroxy-6-naphthoic acid, polyaniline (PAN), polypyrrole (PPy), polythiophene (PT), polyphenylene, sodium polystyrene sulfonate (PSS), cellulose, starch, silicone rubber, acrylonitrile-butadiene-styrene copolymer (ABS), derivatives of the above materials, cross-linked products of the above materials, and copolymers of the above materials.

In some embodiments, the polymer-based composite material includes the polymer material and an additive, wherein the additive includes one or more selected from metal materials and inorganic non-metal materials. The present application has no specific restrictions on the types of metal materials and inorganic non-metal materials, and they can be selected according to actual needs.

In some embodiments, optionally, the thickness H ₁ μm of the conductive layer satisfies 0.2≤H ₁ ≤8. For example, H ₁ may be 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8 or any range consisting of the above values. More optionally, 1≤H ₁ ≤5. In this way, the battery can have good electrochemical properties while improving the safety performance of the battery, for example, the battery can have a longer service life. And the following situations can be effectively avoided: when the conductive layer is too thin, on the one hand, it is not conducive to production and preparation, and on the other hand, there is a risk of being crushed during the cold pressing process; when the conductive layer is too thick, it may not be able to effectively improve the safety performance of the battery.

The positive electrode current collector may be composed only of a conductive layer, or, in addition to the conductive layer, the positive electrode current collector may also include an organic support layer, and the conductive layer is arranged on at least one surface of the organic support layer. In some embodiments, the conductive layer is arranged on one of the surfaces of the organic support layer. In some embodiments, the conductive layer is arranged on both surfaces of the organic support layer. It should be noted that the thickness parameter of the conductive layer refers to the thickness parameter of the conductive layer located on a single side of the organic support layer, or, when the positive electrode current collector is composed only of a conductive layer, the thickness parameter of the conductive layer is the thickness parameter of the positive electrode current collector. When the conductive layer is arranged on both sides of the organic support layer, the thickness of the conductive layer on both sides may be the same or different; the material of the conductive layer on both sides may be the same or different. In addition, when the conductive layer is arranged on both sides of the organic support layer, the parameters of the conductive layer on any one side (such as thickness, material, etc.) meet the requirements of this application, that is, it is considered to fall within the scope of protection of this application.

In some embodiments, optionally, the thickness H ₁ μm of the conductive layer and the thickness H ₂ μm of the organic support layer satisfy 0.1≤H ₁ /H ₂ ≤1. For example, H ₁ /H ₂ may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, or a range consisting of any of the above values. More optionally, 0.1≤H ₁ /H ₂ ≤0.8, 0.2≤H ₁ /H ₂ ≤0.6. In this way, the battery can have good electrochemical properties while improving the safety performance of the battery, for example, the battery can have a longer service life. And the following situations can be effectively avoided: when H ₁ /H ₂ is too small, there is a risk of the composite current collector being crushed during the cold pressing process; when H ₁ /H ₂ is too large, the safety performance of the battery may not be effectively improved.

In some embodiments, optionally, the thickness H ₂ μm of the organic support layer satisfies 1≤H ₂ ≤10. For example, H ₂ may be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10 or any range thereof. Optionally, 4≤H ₂ ≤7. In this way, the battery safety performance can be improved while the battery has high energy density.

In some embodiments, optionally, the total thickness of the positive electrode current collector is H ₀ μm satisfying 5≤H ₀ ≤15. For example, H ₀ may be 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15 or any range consisting of the above values. More optionally, 9≤H ₀ ≤15. In the present application, the total thickness of the positive electrode current collector refers to the sum of the thickness of the organic support layer and the conductive layer located on both sides of the organic support layer.

The inventors of the present application also found during the research process that the elongation at break S ₀ of the positive electrode current collector is related to the total thickness H ₀ μm of the positive electrode current collector, the concentration C ₁ mol/L of the first anion, and the concentration C ₂ mol/L of the second anion. When C ₁ /C ₂ is larger, H ₀ is larger, and the elongation at break S ₀ of the positive electrode current collector is larger.

The elongation at break of the positive current collector refers to the rate of change of its length when it is stretched when it breaks. By comparing the normal positive current collector and the corroded positive current collector, it can be seen that when the tensile force is equivalent, the corroded positive current collector will break when the stretched length is small due to its own defects, so the elongation at break is small. In addition to being related to whether it is corroded, the elongation at break of the positive current collector is also related to its own thickness. The thicker the positive current collector, the greater its elongation at break. When the elongation at break of the positive current collector in the battery is small, it means that under the same force, the positive electrode sheet is more likely to break. After the positive electrode sheet breaks, the positive active material on the positive electrode sheet can no longer be used, which leads to a significant reduction in the capacity of the battery and a significant decline in the cycle performance; in addition, the broken positive electrode sheet is conductive, and when it contacts the negative electrode sheet, it will directly cause a short circuit in the battery, causing safety hazards and affecting the safety performance of the battery.

The inventors of the present application also unexpectedly discovered during the research process that when the battery also satisfies 5S ₀ –(H ₀ /10)≤C ₁ /C ₂ ≤100S ₀ +(H ₀ /9), the influence of corrosion of the conductive layer on the safety performance and electrochemical performance of the battery can be further reduced, thereby making the battery have better safety performance and electrochemical cycle performance.

In some embodiments, optionally, the elongation at break S ₀ of the positive electrode current collector satisfies 2%≤S ₀ ≤3.5%. For example, S ₀ may be 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5% or any range thereof.

In some embodiments, the positive electrode active material layer includes a positive electrode active material.

When the battery of the present application is a lithium-ion battery, the positive electrode active material may include, but is not limited to, one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and their respective modified compounds. Examples of the lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. Examples of the lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and their respective modified compounds.

In some embodiments, in order to further improve the energy density of the battery, the positive electrode active material for the lithium ion battery may include one or more of lithium transition metal oxides of the general formula LiNi _x Co _y M _z O _2-p _Ap , LiMn ₂ O ₄ , aLi ₂ MnO ₃ ·(1-a)LiQO ₂ and their respective modified compounds. In the general formula LiNi _x Co _y M _z O _2-p _Ap , M includes one or more selected from Mn, Al, Mg, Cu, Zn, Zr, Fe, Sn, B, Ga, Cr, Sr, V and Ti, A includes one or more selected from N, F, S and Cl, 0≤x≤1, 0≤y≤1, 0≤z≤1, x+y+z＝1, 0≤p≤1. In the general formula aLi ₂ MnO ₃ ·(1-a)LiQO ₂ , Q includes one or more selected from Ni, Co, Mn, Fe, Ti, Cr and Zr, and 0＜a＜1.

As an example, a positive electrode active material for a lithium ion battery may include _one _or _more of _LiCoO2 , _LiNiO2 , _LiMnO2 _, LiMn2O4 _, LiNi1/ _3Co1 _/ 3Mn1/ _3O2 ₍ NCM333 ₎ _, _{LiNi0.5Co0.2Mn0.3O2} ₍ NCM523 ₎ _, _{LiNi0.6Co0.2Mn0.2O2} ₍ NCM622), LiNi0.8Co0.1Mn0.1O2 (NCM811), _{LiNi0.85Co0.15Al0.05O2} _, _LiMn2O4 , _aLi2MnO3 ·( ₁ -a ₎ _LiMnO2 _, _LiFePO4 _, _and _LiMnPO4 .

When the battery of the present application is a sodium ion battery, the positive electrode active material may include but is not limited to one or more of sodium-containing transition metal oxides, polyanion materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.) and Prussian blue materials.

As an example, the positive electrode active material for a sodium ion battery may include _one or _more _of _NaFeO2 , _NaCoO2 , _NaCrO2 , _NaMnO2 , NaNiO2 _, _NaNi1 /2Ti1/ _2O2 _{, NaNi1/2Mn1/2O2, Na2/3Fe1} _/ _3Mn2 _/ _3O2 _, _NaNi1 / _3Co1 _/ _3Mn1 /3O2, _NaFePO4 , _NaMnPO4 , _NaCoPO4 , Prussian blue-based materials, and materials of the general _formula _XpM'q ( _PO4 ) _rOxY3 _-x . In the general formula _XpM'q ( _PO4 ) _rOxY3 _-x , 0＜p≤4, 0＜q≤2, 1≤r≤3, 0≤x≤2, X includes one or more selected from H ⁺ , Li ⁺ , Na ⁺ , K ⁺ and _NH4 ⁺ , _M ' is _a transition metal cation, optionally including one or more selected from V, Ti, Mn, Fe, Co, Ni, Cu and Zn, and Y is a halogen anion, optionally including one or more selected from F, Cl and Br.

In the present application, the modified compound of each positive electrode active material mentioned above may be a compound obtained by doping and/or surface coating the positive electrode active material.

In some embodiments, the positive electrode active material layer may further include a positive electrode conductive agent. The present application has no particular limitation on the type of the positive electrode conductive agent. As an example, the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the positive electrode active material layer may further include a positive electrode binder. The present application has no particular restrictions on the type of the positive electrode binder. As an example, the positive electrode binder may include one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resin.

The positive electrode active material layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder and any other components in a solvent and stirring them uniformly. The solvent can be N-methylpyrrolidone, but is not limited thereto.

The positive electrode sheet of the present application is described below with reference to the accompanying drawings.

6 is a schematic diagram of an embodiment of the positive electrode sheet 10 of the present application. As shown in FIG6 , the positive electrode sheet 10 includes a positive electrode current collector 101 and a positive electrode active material layer 102 disposed on both surfaces of the positive electrode current collector 101, the positive electrode current collector 101 includes an organic support layer 1012 and a conductive layer 1011 disposed on both surfaces of the organic support layer, and the conductive layer 1011 is disposed between the organic support layer 1012 and the positive electrode active material layer 102.

7 is a schematic diagram of another embodiment of the positive electrode plate 10 of the present application. As shown in FIG7 , the positive electrode plate 10 includes a positive electrode current collector 101 and a positive electrode active material layer 102 disposed on one surface of the positive electrode current collector 101, the positive electrode current collector 101 includes an organic support layer 1012 and a conductive layer 1011 disposed on one surface of the organic support layer, and the conductive layer 1011 is disposed between the organic support layer 1012 and the positive electrode active material layer 102.

[Negative electrode]

The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. For example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode active material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

In some embodiments, the negative electrode active material layer includes a negative electrode active material. The negative electrode active material may be a negative electrode active material for a battery known in the art. As an example, the negative electrode active material may include, but is not limited to, one or more of natural graphite, artificial graphite, mesophase microcarbon beads, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and lithium aluminum alloys. The silicon-based material may include one or more selected from elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. The tin-based material may include one or more selected from elemental tin, tin oxide (e.g., SnO, SnO ₂ ) and tin alloy materials (e.g., Li-Sn alloy, Li-Sn-O alloy).

In some embodiments, the negative electrode active material layer may further include a negative electrode conductive agent. The present application has no particular limitation on the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the negative electrode active material layer may further include a negative electrode binder. The present application has no particular limitation on the type of the negative electrode binder. As an example, the negative electrode binder may include one or more selected from styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

In some embodiments, the negative electrode active material layer may further include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

The negative electrode active material layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder and optional auxiliary agent in a solvent and stirring them uniformly. The solvent can be N-methylpyrrolidone or deionized water, but is not limited thereto.

The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode active material layer. For example, in some embodiments, the negative electrode plate described in the present application also includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode collector and the negative electrode active material layer and disposed on the surface of the negative electrode collector; in some embodiments, the negative electrode plate described in the present application also includes a protective layer covering the surface of the negative electrode active material layer.

[Isolation film]

The separator is located between the positive electrode and the negative electrode, and mainly prevents the positive electrode and the negative electrode from short-circuiting, while allowing active ions to pass through. The present application has no particular restrictions on the type of separator, and any known porous structure separator with good chemical stability and mechanical stability can be selected.

In some embodiments, the material of the isolation membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer are the same or different.

Preparation

The present application also provides a method for preparing a battery, comprising the following

steps

1 and 2.

The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, and the positive electrode current collector includes a conductive layer.

In some embodiments, in step 1, the positive electrode current collector further includes an organic support layer, the conductive layer is disposed on at least one surface of the organic support layer, and the conductive layer is also disposed between the organic support layer and the positive electrode active material layer, the thickness of the organic support layer is H ₂ μm, the total thickness of the positive electrode current collector is H ₀ μm, and the elongation at break of the positive electrode current collector is S ₀ .

In some embodiments, the method further comprises: step 3, selecting batteries that meet at least one of the following conditions (1) to (9) from the batteries obtained in step 2,

(1) 0.2 ≤ H ₁ ≤ 8,

(2)1≤H ₁ ≤5,

(3) 0.1 ≤ C ₁ ≤ 1,

(4) 0.1 ≤ C ₂ ≤ 1.5,

(5) 0.5 ≤ C ₂ ≤ 1.5,

(6) 0.6 ≤ C ₁ + C ₂ ≤ 2.5,

(7) 0.6 ≤ C ₁ + C ₂ ≤ 2.0,

(8) 0.1 ≤ C ₂ /C ₁ ≤ 5,

(9)0.5≤C ₂ /C ₁ ≤5.

In some embodiments, the method further comprises: step 4, selecting batteries that meet at least one of the following conditions (1) to (8) from the batteries obtained in step 2 or step 3,

(1) 5S ₀ – (H ₀ /10) ≤ C ₁ /C ₂ ≤ 100S ₀ + (H ₀ /9),

(2) 0.1 ≤ _{H 1} /H ₂ ≤ 1,

(3) 0.2 ≤ _{H 1} /H ₂ ≤ 0.6,

(4) _1≤H2≤10 ,

(5) _4≤H2≤7 ,

(6)5≤H ₀ ≤15,

(7) 9≤H ₀ ≤15,

(8) 2% ≤ _{S 0} ≤ 3.5%.

In some embodiments, in step 1, the preparation method of the battery is well known. As an example, the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly through a winding process and/or a lamination process, and the electrode assembly is placed in an outer package, and the electrolyte is injected after drying. After vacuum packaging, standing, forming, shaping and other processes, a battery cell is obtained. Multiple battery cells can also be further connected in series, in parallel or in mixed connection to form a battery module. Multiple battery modules can also be connected in series, in parallel or in mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.

Electrical devices

The present application also provides an electrical device, which includes the battery of the present application. The battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

The electrical device may select a specific type of battery according to its usage requirements, such as a battery cell, a battery module or a battery pack.

Fig. 8 is a schematic diagram of an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electric device for high power and high energy density, a battery pack or a battery module can be used as a power source.

As another example, the electric device may be a mobile phone, a tablet computer, a notebook computer, etc. The electric device is usually required to be light and thin, and a battery cell may be used as a power source.

Example

The following examples describe the disclosure of the present application in more detail, and these examples are only for illustrative purposes, as it is obvious to those skilled in the art that various modifications and variations are made within the scope of the disclosure of the present application. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the instruments used in the examples are commercially available.

The batteries of Examples 1-17 and Comparative Examples 1-3 were prepared according to the following method.

Preparation of electrolyte

In a glove box filled with argon (water content <10ppm, oxygen content <1ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a mass ratio of 30:70 to obtain an organic solvent, then 2wt% of vinyl carbonate (VC) was added to the organic solvent, and then fully dried lithium salt was added to the organic solvent to prepare an electrolyte. The types and concentrations of lithium salts are shown in Table 1.

Preparation of positive electrode

The aluminum foil is placed in a mechanical roller and rolled into a conductive layer of a predetermined thickness by applying a pressure of 20 tons to 40 tons; then a mixed solution of polyvinylidene fluoride (PVDF) and NMP is coated on the surface of the organic support layer polyethylene terephthalate (PET) after surface cleaning; finally, the conductive layer of the predetermined thickness is bonded to the two surfaces of the organic support layer and dried to make it tightly bonded to obtain a positive electrode current collector. The specific thickness parameters of the conductive layer and the organic support layer are shown in Table 2.

The positive electrode active material LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM523), the conductive agent carbon black (Super P), and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in a proper amount of solvent NMP at a mass ratio of 80:10:10 to form a positive electrode slurry with a solid content of 50wt%; the positive electrode slurry is uniformly coated on the surface of the positive electrode collector prepared above, and after drying and cold pressing, a positive electrode sheet is obtained.

Preparation of negative electrode

The negative electrode active material graphite, the conductive agent carbon black (Super P), the thickener sodium carboxymethyl cellulose (CMC) and the binder styrene butadiene rubber (SBR) are fully stirred and mixed in a proper amount of solvent deionized water at a mass ratio of 80:15:3:2 to form a negative electrode slurry with a solid content of 30wt%; the negative electrode slurry is evenly coated on the surface of the negative electrode collector copper foil, and after drying and cold pressing, a negative electrode sheet is obtained.

Preparation of isolation membrane

A porous polyethylene film with a thickness of 16 μm was used as the separator.

Preparation of batteries

The positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in an outer package, and after drying, the electrolyte is injected, and after vacuum packaging, standing, forming, shaping and other processes, a soft-pack battery is obtained.

Table 1

Table 2

Test Section

(1) Acupuncture test

At 25°C, charge the battery at 1C constant current to 4.2V, then charge at 4.2V constant voltage to a current less than or equal to 0.05C.

A 3mm high-temperature resistant steel needle is used to pierce the center of the battery surface at a speed of 0.1mm/s until the battery runs out of control, and the status of the battery when thermal runaway occurs is recorded.

(2) Cyclic performance test

At 25°C, charge the battery to 4.2V at 1C constant current, then charge at 4.2V constant voltage until the current is less than or equal to 0.05C. At this time, the battery is fully charged. Record the charging capacity at this time, which is the charging capacity of the first cycle. After the battery is left to stand for 5 minutes, discharge it to 2.8V at 1C constant current. This is a cyclic charge and discharge process. Record the discharge capacity at this time, which is the discharge capacity of the first cycle. Perform a cyclic charge and discharge test on the battery according to the above method, and record the discharge capacity after each cycle. Capacity retention rate (%) of battery after 500 cycles at 25°C = discharge capacity after 500 cycles/discharge capacity of the first cycle × 100%. For accuracy, take the average value of 5 parallel samples as the test result.

table 3

It can be seen from the test results in Table 3 that by adjusting the relationship between the thickness of the conductive layer H ₁ μm, the concentration of the first anion C ₁ mol/L and the concentration of the second anion C ₂ mol/L to satisfy 0.2×(C ₂ /C ₁ )≤H ₁ ≤(C ₂ /C ₁ )+3, and optionally satisfying 0.2×(C ₂ /C ₁ )+0.2≤H ₁ ≤(C ₂ /C ₁ )+2, the safety performance and cycle performance of the battery can be significantly improved. At this time, the probability of fire in the battery is significantly reduced, and the adverse effect of increased corrosion caused by the reduction in the thickness of the conductive layer on the battery cycle performance can also be significantly reduced.

Based on the test results of Example 1, Example 11 and Comparative Example 1, it can be learned that when the electrolyte composition is the same, since the conductive layer of Comparative Example 1 is thinner, even if the conductive layer is slightly corroded by the electrolyte, it will significantly affect the safety performance and cycle performance of the battery.

Based on the test results of Examples 3, 6-9 and Comparative Example 2, it can be learned that when the electrolyte composition is the same, due to the thicker conductive layer of Comparative Example 2, 0.2×(C ₂ /C ₁ )+0.2≤H ₁ ≤(C ₂ /C ₁ )+2 is not satisfied. At this time, the conductivity of the positive electrode collector is relatively strong, and even if an organic support layer is used, the short circuit between the positive and negative electrodes cannot be effectively prevented, which leads to poor safety performance of the battery. In addition, since the conductive layer of Comparative Example 2 is relatively thick, it is not conducive to heat dissipation during the cycle process. At this time, there are more side reactions inside the battery, and the cycle performance of the battery is also poor.

Comparative Example 3 uses ordinary 12μm thick aluminum foil as the positive electrode current collector, which has low resistance and good conductivity. Therefore, the positive and negative electrodes are prone to short circuit during the needle puncture test, which leads to poor safety performance of the battery. At the same time, compared with the composite current collector formed by the conductive layer and the organic support layer, the positive electrode current collector using pure aluminum foil has poor thermal insulation performance, and thus the kinetic performance of the positive electrode side of the battery is poor. The positive electrode has a large resistance to lithium insertion and extraction during charging and discharging, which is easy to cause more side reactions, so the battery cycle performance is also poor.

Based on the test results of Examples 1-17, it can be seen that when the battery further satisfies 5S ₀ –(H ₀ /10)≤C ₁ /C ₂ ≤100S ₀ +(H ₀ /9), it is beneficial to further improve the safety performance and cycle performance of the battery.

It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

A battery comprises a positive electrode plate and an electrolyte, wherein:

The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode current collector comprises a conductive layer.

The electrolyte includes a solvent and a solute, wherein the solute is an ionic salt formed by a cation and an anion, wherein the cation includes one or more selected from alkali metal cations and alkaline earth metal cations, and optionally includes one or more selected from lithium ions, sodium ions and potassium ions, and the anion includes a first anion and a second anion, wherein the first anion includes a hexafluorophosphate anion, and the second anion includes one or more selected from anions represented by Formula 1 and anions represented by Formula 2, R 1 , R 2 , and R 3 each independently represent a fluorine atom or a C1-C5 fluorine-containing alkyl group, and R 1 and R 2 may also be bonded to form a ring,

The thickness of the conductive layer is H 1 μm, the concentration of the first anion in the electrolyte is C 1 mol/L, the concentration of the second anion is C 2 mol/L, and the battery satisfies 0.2×(C 2 /C 1 )≤H 1 ≤(C 2 /C 1 )+3.
The battery according to claim 1, wherein 0.2×(C 2 /C 1 )+0.2≤H 1 ≤(C 2 /C 1 )+2.
The battery according to claim 1 or 2, wherein

0.2≤H 1 ≤8, optionally, 1≤H 1 ≤5; and/or,

0.1≤C 1 ≤1; and/or,

0.1≤C 2 ≤1.5. Optionally, 0.5≤C 2 ≤1.5.
The battery according to any one of claims 1 to 3, wherein

0.6≤C 1 +C 2 ≤2.5, optionally, 0.6≤C 1 +C 2 ≤2.0; and/or,

0.1≤C 2 /C 1 ≤5. Optionally, 0.5≤C 2 /C 1 ≤5.
The battery according to any one of claims 1 to 4, wherein the positive electrode current collector further comprises an organic support layer, the conductive layer is disposed on at least one surface of the organic support layer, and the conductive layer is further disposed between the organic support layer and the positive electrode active material layer.
The battery according to claim 5, wherein the thickness of the organic support layer is H 2 μm, and the battery satisfies 0.1≤H 1 /H 2 ≤1, and optionally, 0.2≤H 1 /H 2 ≤0.6.
The battery according to claim 5 or 6, wherein the thickness of the organic support layer is H 2 μm, 1≤H 2 ≤10, optionally, 4≤H 2 ≤7.
The battery according to any one of claims 5 to 7, wherein the total thickness of the positive electrode current collector is H 0 μm, 5≤H 0 ≤15, optionally, 9≤H 0 ≤15.
The battery according to any one of claims 5 to 8, wherein the total thickness of the positive electrode current collector is H 0 μm, the elongation at break of the positive electrode current collector is S 0 , and the battery satisfies 5S 0 – (H 0 /10) ≤ C 1 /C 2 ≤ 100S 0 + (H 0 /9).
The battery according to claim 9, wherein 2%≤S 0 ≤3.5%.
The battery according to any one of claims 5 to 10, wherein the organic support layer comprises one or more of a polymer material and a polymer-based composite material,

The polymer material includes one or more selected from polyolefins, polyalkynes, polyesters, polycarbonates, polyacrylates, polyamides, polyimides, polyethers, polyalcohols, polysulfones, polysulfur nitrides, polysaccharide polymers, amino acid polymers, aromatic ring polymers, aromatic heterocyclic polymers, epoxy resins, phenolic resins, polyurethanes, thermoplastic elastomers, rubbers, derivatives of the above materials, crosslinked products of the above materials, and copolymers of the above materials, and optionally includes one or more selected from polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyacetylene, polyparaffin, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride ... One or more of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polymethyl methacrylate, polycaprolactam, polyhexamethylene adipamide, poly(p-phenylene terephthalamide), polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, polyvinyl alcohol, poly-4-hydroxybenzoic acid, poly-2-hydroxy-6-naphthoic acid, polyaniline, polypyrrole, polythiophene, polyphenylene, sodium polystyrene sulfonate, cellulose, starch, silicone rubber, acrylonitrile-butadiene-styrene copolymer, derivatives of the above materials, crosslinked products of the above materials, and copolymers of the above materials,

The polymer-based composite material comprises the polymer material and an additive, wherein the additive comprises one or more selected from metal materials and inorganic non-metallic materials.
The battery according to any one of claims 1 to 11, wherein the conductive layer comprises one or more selected from metal materials, optionally comprising one or more selected from aluminum, silver, nickel, titanium, stainless steel, aluminum alloy, silver alloy, nickel alloy and titanium alloy.
The battery according to any one of claims 1 to 12, wherein

R 1 , R 2 , and R 3 each independently represent a fluorine atom, a trifluoromethyl group, a pentafluoroethyl group, or a heptafluoropropyl group; and/or,

R1 and R2 are the same.
The battery according to any one of claims 1 to 13, wherein the electrolyte further comprises a third anion, and the third anion comprises one or more selected from tetrafluoroborate anion, difluorooxalatoborate anion, dioxalatoborate anion, difluorophosphate anion, difluorobisoxalatophosphate anion and tetrafluorooxalatophosphate anion.
The battery according to any one of claims 1 to 14, wherein the battery further comprises a negative electrode sheet and a separator, and the separator is located between the positive electrode sheet and the negative electrode sheet.
A method for preparing a battery comprises the following steps:

Step 1: Assemble the positive electrode sheet, separator, negative electrode sheet and electrolyte into a battery.

The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode current collector comprises a conductive layer.

The electrolyte includes a solvent and a solute, wherein the solute is an ionic salt formed by a cation and an anion, wherein the cation includes one or more selected from alkali metal cations and alkaline earth metal cations, and optionally includes one or more selected from lithium ions, sodium ions and potassium ions, and the anion includes a first anion and a second anion, wherein the first anion includes a hexafluorophosphate anion, and the second anion includes one or more selected from anions represented by Formula 1 and anions represented by Formula 2, R 1 , R 2 , and R 3 each independently represent a fluorine atom or a C1-C5 fluorine-containing alkyl group, and R 1 and R 2 may also be bonded to form a ring,

The thickness of the conductive layer is H 1 μm, the concentration of the first anion in the electrolyte is C 1 mol/L, and the concentration of the second anion is C 2 mol/L;

Step 2, selecting from the batteries obtained in step 1 batteries that satisfy 0.2×(C 2 /C 1 )≤H 1 ≤(C 2 /C 1 )+3, and optionally batteries that satisfy 0.2×(C 2 /C 1 )+0.2≤H 1 ≤(C 2 /C 1 )+2.
The method according to claim 16, wherein the method further comprises: step 3, selecting batteries that meet at least one of the following conditions (1) to (9) from the batteries obtained in step 2,

(1) 0.2 ≤ H 1 ≤ 8,

(2)1≤H 1 ≤5,

(3) 0.1 ≤ C 1 ≤ 1,

(4) 0.1 ≤ C 2 ≤ 1.5,

(5) 0.5 ≤ C 2 ≤ 1.5,

(6) 0.6 ≤ C 1 + C 2 ≤ 2.5,

(7) 0.6 ≤ C 1 + C 2 ≤ 2.0,

(8) 0.1 ≤ C 2 /C 1 ≤ 5,

(9)0.5≤C 2 /C 1 ≤5.
The method according to claim 16 or 17, wherein in step 1, the positive electrode current collector further comprises an organic support layer, the conductive layer is disposed on at least one surface of the organic support layer, and the conductive layer is further disposed between the organic support layer and the positive electrode active material layer, the thickness of the organic support layer is H 2 μm, the total thickness of the positive electrode current collector is H 0 μm, and the elongation at break of the positive electrode current collector is S 0 .
The method according to claim 18, wherein the method further comprises: step 4, selecting a battery satisfying at least one of the following conditions (1) to (8) from the batteries obtained in step 2 or step 3,

(1) 5S 0 – (H 0 /10) ≤ C 1 /C 2 ≤ 100S 0 + (H 0 /9),

(2) 0.1 ≤ H 1 /H 2 ≤ 1,

(3) 0.2 ≤ H 1 /H 2 ≤ 0.6,

(4) 1≤H2≤10 ,

(5) 4≤H2≤7 ,

(6)5≤H 0 ≤15,

(7) 9≤H 0 ≤15,

(8) 2% ≤ S 0 ≤ 3.5%.
An electrical device, comprising the battery according to any one of claims 1 to 15 or a battery prepared by the method according to any one of claims 16 to 19.